I think my black molly is suffering. I don't know if it's male or female. It's bloated (compared to when I got it a year ago) and it's scales are now raised. It can't seem to find the food when I feed the tank. It hangs around the top looking for it, but never actually eats any. It swims the entire tank oherwise. I have a 50 gallon with an Eheim filter system. There are about 6 other fish in the tank: 4 tiger barbs, another fish that looks like a tiger barb but it's orange and white, an orange fish with black fins (another molly perhaps), a small catfish, a betta, and one of those sucker fish. I haven't checked the water quality recently (my kit has gone missing), and I haven't done a water change in months. I get so much evaporation here that I have to add water every few days. I'm using distilled water (our tap water is very poor due to drought conditions) and the pet store had me add back the essential minerals with a product by Kent Freshwater called R/O Right. None of the other fish seem affected. Is this dropsy or something else? How do I treat dropsy if that is the problem?